Doing trade runs is the number one choice.
You can also farm, which what I am doing now.
In farming you have to know first what is in high demand in your server to grow.
You can also farm monsters in Auroria to get the Auroria armor and sell them, but this will also depend on your server
you have to see if there is a demand for them and do they sell for good amount of money
You can make money through the AH
From time to time check the AH and you will find some items (like, Worker's com, XP Bosst, etc.) listed for a very low price. buy and resell
You can also buy item with high quantities (like 1000) and break them down to smaller quantities and list them
you have to know there are a lot of low level player and don't have money, so they can't afford to buy 1000 of the same item
specially if they need 50 (some low level player when making trad backs, it is easier for them to buy the ingredient from AH instead of farming them)
This is all I know, I am not an expert in the game

good luck